A standard yarn-winding apparatus has a support that holds a spool centered on a spool axis for rotation about this axis, a friction-drive roller that is rotated at a constant speed and that radially engages the spool to rotate it, and guides for feeding the yarn to the spool so it is wound thereon as the spool rotates. The guides includes a reciprocating traverse that lays the yarn in even layers on the rotating spool.
Synthetic-resin yarns are very sensitive to their treatment parameters, as for instance their temperature, amount of stretch, tension, and the like. Such a synthetic-resin yarn can take dye differently, develop different surface characteristics, and otherwise alter significantly to affect the appearance and feel of the finished goods, whether woven or knitted, that they are incorporated in if any of these treatment parameters varies excessively.
It has been determined that the yarn must be pulled at the very start of a winding operation with a tension that is somewhat greater than that used for the balance of the winding up. This increased tension, which must not be great enough to snap the yarn, pulls the yarn tight and causes it to move smoothly afterward.
It is therefore known from German patent document 2,432,166 of J. Bock et al to provide the friction-drive roller with an annular raised region of greater diameter than the body of the roller that is positioned offset axially from the region where the yarn body will be formed. Thus to start with the spool will be driven slightly faster than normal. Once, however, the yarn body has built up on the spool sufficiently that it directly contacts the friction roller, the spool-rotation speed is reduced again and depends on the peripheral velocity of the body of the friction roller, not of its raised rim. Such a system is very simple, but the first 1000 m or so of yarn is wound at a tension that is different from that of the balance of the yarn and, therefore, will behave differently in subsequent treatment.
In U.S. Pat. No. 3,831,362 of C. J. Dudzik the spool is provided at one end with a large-diameter rim, or such a rim is provided on the support carrying the spool. The friction-drive roller is cylindrical so that at the start of winding it contacts only this large-diameter rim so that the peripheral speed of the spool is smaller than that of the friction roller. This peripheral speed increases as the yarn body grows until the yarn body gets bigger than the rim and the drive roller loses contact with the rim, whereupon the peripheral speed stays the same for the rest of the winding operation. Thus the innermost layers of yarn are wound somewhat more loosely than the outer ones, again producing nonuniform results during subsequent treatment.
In German patent document 3,009,714 of Y. Inouye and British patent 1,175,965 other winding systems are shown, but that do not give a high starting speed to get the filament up to speed while at the same time winding it on the spool with uniform tension.